Generally, internal combustion engines are provided with an external EGR device for recirculating a part of exhaust gas to an intake side. There has been known an EGR cooler disposed in an EGR pipe in an external EGR device to cool an EGR gas. Further, there has been generally known an intercooler disposed upstream of an intake port in an internal combustion engine equipped with a supercharger. In this case, condensed water is generated in the gas passage through which the EGR gas passes.
For example, Patent Literature 1 describes a technique of controlling the cooling performance of an EGR cooler so as to make the temperature at the outlet of the EGR cooler to be equal to or lower than a necessary temperature coincident to a saturated vapor partial pressure, in order to restrict the generation of condensed water in an intercooler.
However, in an actual EGR system, an EGR gas flows into an EGR cooler and, thereafter, until it is introduced into cylinders, condensed water may be generated at a plurality of portions.